Many industrial processes entail the production of materials in a continuous fashion, such as the manufacture of carpet, vinyl sheet goods, roofing material, textiles, plastic sheeting, tiles, and even steel. Some of these materials may contain patterns that are introduced for aesthetic purposes, and whose regularity and consistency in both short and long length scales, along and across the continuous sheet, are extremely important for the value, utility and merchantability of the product. An example is patterned carpeting, where the straightness of the pattern and freedom from bowing, skewing and other pattern defects is essential to the aesthetics, and to the proper and efficient seaming and installation of the product. The introduction of fiducial markings that can be sensed by an automated system will provide the capability to provide real-time monitoring and potentially correction of patterns errors in materials such as carpeting and other sheet goods.
Patterned carpet is typically formed using fibers that are tufted, using a “tufting machine” into a woven fabric known as primary backing. The tufted fibers form the “face fiber” of the carpet and are principally responsible for the esthetics and performance of the product.
An example of tufted carpet is shown in FIG. 2. The pattern of the carpet is established by tufting different types or colors of fibers into different locations on the primary backing. Following tufting, the primary backing is “finished” by bonding the tufted primary backing to a heavier, coarse woven fabric known as secondary backing. Such a process is performed on a “finishing line.” Once the carpet has been finished it is highly rigid composite structure and pattern errors cannot be corrected without expensive and time-consuming “power stretching” during the installation process. Thus, there is considerable impetus for the development of a method and device for sensing pattern errors in carpet and correcting said errors prior to finishing.
The present invention permits the introduction of fiducial marks during the manufacture of the carpet that are invisible to the consumer but are none-the-less visible to equipment during the manufacture of the carpet. Moreover, the present invention is particularly useful in detecting fiducial marks in carpeting or other patterned materials, where defects in patterned components of the materials can affect the aesthetics, production and/or installation of the final product.